Final Diagnosis -- Lymphoplasmacyte-rich Meningioma

FINAL DIAGNOSIS:

MULTIPLE, en plaque, LYMPHOPLASMACYTE-RICH MENINGIOMA

DISCUSSION:

Lymphoplasmacyte-rich meningioma was first described in 1971 by Banerjee and Blakwood (1). Horten et al. (2) reported five cases of such meningioma and observed that the proportion of neoplastic meningothelial cells is quite variable in relation to the plasma cell component. Plasma cells may predominate and only nests of epithelial cells remain, obscuring the underlying meningioma pattern. This variant differs from typical meningiomas, in which the infiltration of lymphocytes is usually discreet or may form perivascular cuffs. Stam et al. (3) affirmed that plasma cell infiltrates were not tumoral in origin, since these cells produced almost all classes of immunoglobulins. Some neuropathological studies have demonstrated that the inflammatory infiltrates may consist predominantly of T-lymphocytes (4,5).

Meningiomas constitute between 13 and 26% of primary intracranial tumors (6). Spinal meningiomas form only a small proportion, approximately 12%, of all meningiomas (7). Ten percent of meningiomas are multiple and occur most commonly with type-2 neurofibromatosis, although they can be found without this condition (6, 8). In the spinal canal, the thoracic region is more often involved than other levels. Meningiomas can be related or attached to a nerve root and rarely is the tumor entirely extradural (9). Another macroscopic variant is the meningioma en plaque, which is not greatly raised above the level of the dura mater, but is prone to invade the adjacent bone, with accompanying hyperostosis (7). Occasionally, they appear more diffuse and may grow en plaque over the convexity of the brain or form a collar-like mass around the spinal cord. They may compress adjacent structures and are more infiltrative of neural tissues.
In our case, the tumor was restricted to the cervical portion of the spinal canal and infiltrated some nerve roots. Another important feature of our case was the growth pattern represented by the en plaque variant associated with multiple tumors, firmly adhered to the internal face of the dura.

Yamaki et al. (10) reported a spinal tumor which presented as an en plaque mass extending from the foramen magnum to C5 and encircled the spinal cord. They obtained positive staining for vimentin and EMA, indicating the meningothelial origin of the tumor. They also showed polyclonal characteristics of plasma cell infiltrates by immunohistochemical staining for kappa- and lambda-light chains.

No protein electrophoresis was performed in our case, but blood abnormalities are found in patients with lymphoplasmacyte-rich meningioma. Plasma cells are thought to secrete immunoglobulins across the blood-brain barrier and after complete removal of the tumor, blood abnormalities tend to disappear as well as reappear with relapse of the tumor (11).

Although the meningothelial component has been confirmed, whether the lesion is primarily neoplastic or simply granulomatous with a secondary meningeal reaction is an important question that remains unsolved (10). The exact differentiation between meningothelial hyperplasia and neoplasia, at the present, is probably impossible. The meningiomatous component in the lymphoplasmacyte-rich variant of meningioma may also be secondary to chronic inflammation, a fact that can not be ruled out.

REFERENCES

Banerjee AK, Blackwood W (1971) A subfrontal tumor with the features of plasmocytoma and meningioma. Acta Neuropathol 18: 84-88